The objectives of the research to be conducted are directed at establishing the consequences of long-term exposure to delta-9- THC, the psychoactive ingredient in marijuana, on central nervous system function. The neural system to be investigated in these studies is the hippocampus of the awake freely moving animal. Experiments are described which will examine the effects of intermediate (30 days) and very long-term (8 month) daily exposure to delta-9-THC on well characterized electrophysiological correlates of hippocampal function during the performance of both auditory and spatial discrimination tasks. The research plan is designed to systematically evaluate the effects of delta-9-THC and other cannabinoid derivatives on synaptic and cellular responses in the hippocampus during controlled behavioral performance both during and after long- term exposure to these cannabinoids substances. In particular, a portion of this research strategy is designed to evaluate the implications of recently demonstrated pathological changes in the hippocampus resulting from 8 month exposure to delta-9-THC in rats. The two behavioral protocols utilized to assess these changes have been shown to provoke specific changes in hippocampal cell firing.